If you exit comm while in mid-selection, you are left with this selection artifact/sprite (blue rectangle) on your screen. It does not go away until you restart NS and causes ambigueties in your pop-up menu and sensitivity. It is easy to reproduce:
1) enter comm
2) start a selection rectangle
3) while *still depressing* your mouse button and maintaining the selection rectangle, rollover the logout button and release.
Easier method:
1) enter comm
2) start a selection rectangle and maintain it
3) have your teammates or an admin eject you